Choke for shotguns



Nov. 5, 1968 A. DURO CHOKE FOR SHOTGUNS Filed Nov. 2. 1966 F/G. 3A.

"positionl y l q i The spread 'of theushot in Shotguns is limited by the 3,408,762 Patented Nov. 5, 1968 U11-fed Sme. Parent* @me i. 4 claims-icl. 42-19) ABSTRACT F THE DISCLOSURE l Y This invention :relates to' a shotgun choke that' is adjstable by means of a slidahlegrip. Thegripis linked to th'efchoke by screw means having two separate pitches. Linear movement'of vthefgrip rotates the screwme'ans .vhicliin turn causes linear movement of the choke facili- -t'ate'd'4 by"4v th'e mechanical advantage' Vobtaned with the double pitch screw means.

This inventionrelates to'a control for'the choke of shotgu'ns andV particularly to a' control which enables -`the Ishooter to change the choke with the gun in the shooting constriction of the muzzle, universally known as choke There are several models of devices for adaptation to the muzzleof single barreled shotguns and which regulate the choke. For example, shotgun chokes of the7 'prior art must be set before shooting, u suallyby screwinga4A muzzle adapter by hand." l 4 :Y

Itluis an objectiofthis inventionto provide acontrolzfor the chokof Shotguns; which maybe changd'with'the `weapon held to the shoulder.

It is another object of this invention to provide a' shotgun choke control that can'bemanipulated by one hand I on the forestock.

The invention accomplishes these objects by providing a shotgun with either a. barrel slotted longitudinallyon :the end or a slotted muzzle adapter .placed on `thelend of the shotgun barrel. Overthefslotted. section there isplaced p 1.a. movable constricting means `such as a cone frustum. The movable constricting means engages with screw means to force theconstricting means .back and forth Jalong the slotted section. The screw means is activated by an operating rod having a helical section of long pitch. The operating rod is caused to rotate by engaging the helical section of the operating rod with a movable bar having an opening which matches the cross section of the helical section of the operating rod. The bar is caused to move along the helical section of the operating rod by rectilinear movement of a sliding grip attached to the barrel. The sliding grip is mounted under the forestock of the shotgun so that it is in contact with one hand of the shooter.

For a better understanding of the invention reference may be had to the accompanying drawings in which:

FIG. 1 is a partial front elevation of a shotgun employing the teachings of the invention;

FIG. 2 is an elevation of a muzzle adapter;

FIG. 3 is an elevation of a screw means for moving the constricting means of FIG. 4;

FIG. 3A is an end view of the screw means of FIG. 3;

FIG. 4 is a constricting means to be placed over the slotted adapter of FIG. 2;

FIG. 5 is an elevation of an operating rod; and

FIG. 6 is an elevation of the bearing plate which supports one end of the operating rod of FIG. 5.

In the drawings, where like numerals refer to like parts, there is shown an embodiment of the present invention. With particular reference to FIG. 1 there is shown a shotgun 10 with a barrel 12 and a forestock 14. A slotted vmuzzle adapter 16 is rigidly attached to the end of barrel 12 by a'ny suitable means such as screw threads. Muzzle adapter 16 isl provided with a plurality of longitudinal slots 34. Muzzle adapter 16 may be provided with a plurality of transverse slots36, as in chokes of the prior art. The bore of muzzle adapter 16 is at least as large as that of barrel 12. Muzzle adapter 16 is provided with la lateral extension 40. A movable constricting member 18 is slidably mounted over muzzle adapter 16, Constricting member 18 is provided with a lateral extension 38. A screw means 20 is provided to secure movement of constricting member 18 over muzzle adapter 16. An operating rod 22 is provided having one end which fits nonrotatably in screw means 20. Operating rod 22 has a .helical section 24 which is threaded through an opening (not shown) in a' follower 54 of a mov-able bar 26. Movable bar 26 is rigidly attached to a slidably mounted grip 28, that is carried under forestock 14. As stated, grip 28 is) slidably mounted to forestock 14 so that grip 28 may slide along forestock 14. The means for so slidably mounting grip 28 to forestock 14 is well known to the v gunsmith and no particular means, therefore, are shown.

Follower 54 is bent substantially at a right angle to the rest of movable bar 26. The opening in follower 54 25.

through which helical section 24 is threaded is substantially the same cross section of the helical section and has internally helical-shaped surfaces of the same long pitch as the helical section. A bearing plate 30 is provided to support the other end of operating rod 22. Bearing plate 30 is secured with a nut 32 to forestock 14.

With reference to FIG. 2, there is shown the detail of muzzle adapter 16. Longitudinal slots 34 are open ended,

'as at 34a, to define a plurality of muzzle adapter portions 35, so that the desired choke may be obtained by forcing portions 35 together at their free ends. Lateral extension 40 is provided with a circular opening 42, having its axis parallel to barrel 12 and serves as a bearing journal for rotatably holding screw means 20. As shown in FIG. 3, screw means 20 has an endless thread 21 of short pitch. A groove 23 is provided so that screw means 20 may lit and rotate in circular opening 42. As shown in FIG. 3A, the end of screw means 20 nearest groove 23 is provided with a slit 25 of a size to receive one end of operating rod 22. Slit 25 is of a sufficient depth so that in recoil operated Shotguns operating rod 22 may move within slit 25. Slit 2S is so shaped as to prevent relative movement of screw means 20 and operating rod 22 when both are engaged. It should be noted, that in recoilless Shotguns, the invention may be simplied by making screw means 20 and operating rod 22 in one piece.

With reference to FIG. 4, it will be seen that movable constricting member 18 has one end portion 17 which is substantially cylindrical and the other end 19 portion which is substantially that of a frustum of a cone. Cone frustum portion 19 is sized to choke muzzle adapter 16 when forced back upon it. The cylindrical portion 17 has an internal diameter slightly larger than the external diameter of muzzle adapter 16 to allow a sliding iit without effort. A lateral extension 38 is provided with an opening 39 threaded to match the thread of screw means 20. If muzzle adapter 16 has been provided with slots 36, then constricting member 18 is provided with windows 41 that are positioned so as to be over slots 36 when assembled.

In FIG. 5, operating rod 22 is provided with a straight section 27 and helical thread section 24. Straight section 27 is designed to be slightly longer than the recoil distance in an automatic shotgun to permit unimpeded action. Helical section 24 is of long pitch for ease of actuation as will be explained later in the operation of the invention. Near the end of helical section 29 a small shaft 31 is provided to support one end of operating rod 22 f da. as will be described later in reference to A 33 of straight section 27 is adapted to t into slot'25 of screw means 20 of FIG. 3;' and FIG. 3A in the manner a screwdriverfits into a screw head. Itwillbeunderstood that operating rod 22`may be of a crosssectiohther than rectangular. 1'

One may see in FIG. 6 that shaft l31is' supported'` by 'bearing plate 30. Bearing plate 30is providedwitlrfa circular opening 46 for attaching bearing plate' 30 tof'for'earises. may harnas? in thsalove lssfibsfi pparts sucha's' nakir''gthel choking sectioi'irte'g'r'lwth the barrel, omitting the trangverse slots in the muzzle adap ter, omitting the windows in the constricting means, using Numerous 5 other than a cone frustu'mas'Lthe'constricting means, makcure mecijn'c' meats-Oath nv @si @2612.. H 'htte .wing 10 from the spirit a stopfen e f;rtismrerfdeatht an matters containedin thejoregging description or shown in the accompanying drawings shall be interpreted as illustrative and notir'almltligese'."

Whatli'sffclaimedsizi Stege" 'fitr :r Shotguns having a itudina slit bar 26 engagesvwith helicalportion 24 Ofw'operatingrdd 22 causing operating rod 22 to rotateinv Vthe bearing journal in hole 48. The transition from the rectilinear motion of slidably mounted grip 28 land movable bar 26 t'o tlie rotary motion of operating rod 22 is made'easy by the long pitch of the helicalthreads of helical portion'24.

25 l. .2' tisslofgv-9h9k controlf-.ofc'lai' The rotation of operating'rod 22 is transmitted to'sc'rew means 20 which also rotates using hole 42 in muzzle adapter 16 as a bearing. The short pitch of the threads of screw means 20 engaged with threaded hole 39 in movable constricting means 18 causes constricting means 1 8- 30, prifs ifng:

to move backwards or forward a short distance along muzzle adapter 16. The short pitch of the threads'of screw means 20 gives mechanical advantage to exert great force on the slotted barrel segments, such as segment 3 5, to close the muzzle to the desired choked condition.

It can be seen from the drawings that there has been provided a choke control for Shotguns of both the xed barrel and recoil operated types. The choke control of the present invention enables the user to obtain shot spreads ranging from that of a cylindrical bore to a full' choke concentration. The choke control permits `the `choke of a shotgun to be changed between shots without taking the weapon from the shoulder fitting position. Very little effort is required to move the sliding grip along the forestock because of the long pitch of the helical section of the operating rod. It will, therefore, be apparent' that there has been disclosed a `,shotgun choke control that is easier and more convenient to operate than the'shotgun choke control of the prior art.

an operating rod having a helcaltlread oflong 'plt'ih over at least -a portionqof its length "for connecting the sliding grip with said screw means.

means coupl'ed'to "a portion of the "sliding grip'a'dapt'cd y to, engagesaid helical thread orsaid operatingfrd. 3. The' shotgun vchoke c dritrolot claiin furthe1 corn 35 screwmeans is provided with an opening t'o receive-said BENJAMIN A;BORIELT,Febuary"Emimmei.` 

